The present invention relates to power supplies, and more particularly to a programmable multiple output DC-DC isolated power supply with programmable operating characteristics.
Today""s electronic systems often require multiple voltages having varying turn-on and turn-off sequencing requirements. For example, application specific integrated circuits (ASICs) from different manufacturers often require different voltage rails and currents, and different turn-on and turn-off sequencing.
These requirements are increasingly being met by the use of DC-DC converters that are mounted on the printed circuit boards. As a result of technological improvements in component design, DC-DC converters for on-board applications are becoming smaller and more powerful. For example, 50 A, 150 W xc2xc bricks are now available where a few years ago, 25A was the maximum available for the xc2xc brick package size. In this regard, increasing the package size to a xc2xd brick or a full brick allows a commensurate increase in the power that the DC-DC converter package can provide. A xe2x80x9cbrickxe2x80x9d when used in the context of DC-DC converters means the package size of converter. For example, the industry standard package size and footprint of a xc2xc brick is 1.45xe2x80x3xc3x972.28xe2x80x3 by 0.5xe2x80x3.
These newer, higher power DC-DC converters can often be used to supply all the power requirements for some electronic devices. However, both the newer, higher power DC-DC converters as well as the older, lower power, DC-DC converters typically are designed to have set output voltages. In designing the power supply for a circuit board, a DC-DC converter is selected whose output voltage meets a voltage requirement for the circuit board. Appropriate circuitry is then provided to convert the output voltage of the DC-DC converter to other voltage requirements needed as well as provide the other operating characteristics of the power supply for the circuit board. In many electronic devices requiring multiple voltages, the voltages must be powered up in an appropriate sequence and powered down in an appropriate sequence. Alternatively, multiple DC-DC converters, or DC-DC converters having multiple outputs, are used having the requisite voltage outputs. FIG. 1 illustrates diagrammatically the latter approach, which also requires appropriate circuitry to control the turn-on and turn-off sequences and other operating characteristics of the power supply.
Turning to FIG. 1, a prior art on-board (that is, for mounting on a printed circuit board) power supply 10 is shown. Power supply 10 illustratively provides four sources of powerxe2x80x94a 3.3 VDC five amp power source, a 2.5 VDC twenty amp power source, a 1.8 VDC ten amp power source, and a 1.2 V ten amp power source. To do so, power supply 10 has a first DC-DC converter 12 that has a nominal output of 3.3 VDC at eight amps, a second DC-DC converter 14 that has a nominal output of 2.5 VDC at twenty-five amps, a third DC-DC converter 16 that has a nominal output of 1.8 VDC at twenty-five amps and a fourth DC-DC converter 18 that has a nominal output of 1.2 VDC at twenty-five amps. Each DC-DC converter 12, 14, 16, 18 has a power input coupled to a source of DC power that can range from 35 VDC to 75 VDC. DC-DC converters 12, 14, 16, 18 may illustratively be AV45C series DC-DC converters available from ASTEC Power of Andover, Mass. Each DC-DC converter 12, 14, 16, 18 may also be coupled to power supply logic (not shown) that controls the turn-on and turn-off sequences of the power supplied by each DC-DC converter, synchronizes them, and the like.
A problem with the above described on-board power supplies is that during the design and development of a circuit board, the power requirements may change. For example, ASICS from different manufacturers often require different voltages and different turn-on and turn-off sequences of the voltages supplied by the power supply. Consequently, if design changes are made to the circuit board, such as changing an ASIC requirement or replacing an ASIC from one manufacturer with an ASIC from another manufacturer, this may require that the power supply for the circuit board be redesigned. This may require that the layout of the power supply on the circuit board be redone with the resultant time and expense of doing so. Moreover, if this redesign requires replacement of one or more of the DC-DC converters, such as would be the case if one or more of the voltage requirements change, then the stock of the original DC-DC converters on-hand would no longer be of use for that product.
A multi-output DC-DC power supply has programmable operating characteristics that include at least one of voltage levels, mono-phase and multi-phase modes, turn-on and turn-off sequences, voltage tracking, switching frequencies and whether the switching frequencies are synchronized, and thresholds for protection modes and action-if-fault upon detection of a fault. The power supply has a DC-DC converter having an output coupled to a plurality of buck converters. Each buck converter has an output and a control input where the voltage at the output of the buck converter is determined by a duty cycle of at least one pulse width modulated signal provided at the control input of that buck converter. A programmable device has outputs coupled to the control inputs of the buck converters. The programmable device generates the pulse width modulated signals at its outputs for controlling the buck converters to provide voltages corresponding to voltages programmed in the programmable device. The programmable device is programmable to control the programmable operating characteristics.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.